Individuality in male songs of wild black crested gibbons (Nomascus concolor)

This is the first study of vocal individuality in male songs of black crested gibbons. The sound recordings were carried out at two field sites, Pinghe, Ailao Mountains, and Dazhaizi, Wuliang Mountains, both located in Yunnan province, China. A total of 127 coda phrases of 38 male songs bouts of eight individual male gibbons were analyzed. Stepwise discriminant function analysis was used to examine the acoustic individuality of the males. We found that individuality among neighbors was very pronounced. Moreover, individuality within a site (i.e. among neighbors) is higher than among individuals between sites. Our finding suggests that black crested gibbons may actively increase their degree of vocal individuality against that of their immediate neighbors by vocal adjustment.     

人工饲养南黄颊长臂猿行为活动节律的季节性特征

2017年10月-2018年9月,采用瞬时扫描法和目标取样法对南京市红山森林动物园高淳湿地研究中心的南黄颊长臂猿Nomascus gabriellae季节性活动节律进行观察研究,共计扫描4 369次,观察时间累计1 092 h,得到行为数据26 208个,将其行为划分为取食、休息、运动、社会、交配和其他6种。结果表明,休息和运动是南黄颊长臂猿各季节的主要行为类型,其次为取食和社会行为。各行为在不同季节具有明显的节律性,休息一般出现在晨昏和正午;而运动一般出现在上午和下午;取食在各季节存在2个明显高峰,受饲养员喂食时间和频次的影响较大,表现为休息-运动-取食-休息-运动-取食-休息的行为模式。Kruskal-Wallis H分析结果显示,南黄颊长臂猿在不同季节和相同季节不同时段的行为差异有统计学意义:秋、冬季的取食行为明显高于春、夏季,而休息和运动相反。温度、日照、天气、游客量、饲养员日常操作等均影响南黄颊长臂猿的活动节律。     

Sleeping sites, sleeping trees, and sleep-related behaviors of black crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang, Central Yunnan, China

Data on sleep-related behaviors were collected for a group of central Yunnan black crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang, Yunnan, China from March 2005 to April 2006. Members of the group usually formed four sleeping units (adult male and juvenile, adult female with one semi-dependent black infant, adult female with one dependent yellow infant, and subadult male) spread over different sleeping trees. Individuals or units preferred specific areas to sleep; all sleeping sites were situated in primary forest, mostly (77%) between 2,200 and 2,400 m in elevation. They tended to sleep in the tallest and thickest trees with large crowns on steep slopes and near important food patches. Factors influencing sleeping site selection were (1) tree characteristics, (2) accessibility, and (3) easy escape. Few sleeping trees were used repeatedly by the same or other members of the group. The gibbons entered the sleeping trees on average 128 min before sunset and left the sleeping trees on average 33 min after sunrise. The lag between the first and last individual entering the trees was on average 17.8 min. We suggest that sleep-related behaviors are primarily adaptations to minimize the risk of being detected by predators. Sleeping trees may be chosen to make approach and attack difficult for the predator, and to provide an easy escape route in the dark. In response to cold temperatures in a higher habitat, gibbons usually sit and huddle together during the night, and in the cold season they tend to sleep on ferns and/or orchids.     

海南长臂猿的家族群相遇行为观察

海南长臂猿(Nomascus hainanus)是野外研究最少的长臂猿种类之一。在过去的十多年中,只了解其种群数量、种群结构、栖息地和有关于其食物种类的极少量信息。对于世界上最濒危的灵长类之一的海南长臂猿,在长达4年的野外研究中,主要采用扫描取样法和焦点动物取样法观察到了4次海南长臂猿的合群现象,并发现了现存的两群海南长臂猿之间的合群行为不同于其他长臂猿,如白掌长臂猿(Hylobates lar)的合群行为。在海南长臂猿的合群行为中,只观察到了雌雄性成年个体和雄性亚成体以及青年雄性个体之间的鸣叫和追逐行为,而没有发现像白掌长臂猿样的两群体成员间的玩耍和理毛行为,更没有偷情行为和白掌长臂猿那样致命的激烈打斗行为的存在,即只存在着鸣叫行为和竞争性行为。两群体的雌性成年母猿根本就不参与到追逐行为中,它们只是在相距合群行为发生地点20—30m处休息和观望。同时,海南长臂猿相遇的持续时间也不像其他种类的长臂猿那样长,只有24—51min。另外,也没有发生打斗行为。对于海南长臂猿雌雄性成年个体在群体相遇时的行为,我们认为是它们对其领域的保护,而未成年个体则是通过参与这种追逐方式学习如何保护自己今后的领域。     

Duet-splitting and the evolution of gibbon songs

Unlike the great apes and most other primates, all species of gibbons are known to produce elaborate, species-specific and sex-specific patterns of vocalisation usually referred to as "songs". In most, but not all, species, mated pairs may characteristically combine their songs in a relatively rigid pattern to produce coordinated duet songs. Previous studies disagree on whether duetting or the absence of duetting represented the primitive condition in gibbons. The present study compares singing behaviour in all gibbon species. Various vocal characteristics were subjected to a phylogenetic analysis using previously published phylogenetic trees of the gibbon radiation as a framework. Variables included the degree of sex-specificity of the vocal repertoire, the occurrence of solo songs, and the preference for a specific time of day for song-production. The results suggest the following scenario for the evolution of gibbon songs: (1) The last common ancestor of recent gibbons produced duet songs. (2) Gibbon duets probably evolved from a song which was common to both sexes and which only later became separated into male-specific and female-specific parts (song-splitting theory). (3) A process tentatively called "duet-splitting" is suggested to have led secondarily from a duetting species to a non-duetting species, in that the contributions of the pair-partners split into temporally segregated solo songs. This appears to be the first time that a non-duetting animal can be shown to be derived from a duetting form. (4) The return to exclusive solo singing may be related to the isolated island distribution of the non-duetting species.     

A comparative analysis of internal cranial anatomy in the hylobatidae

Craniometric studies on the hylobatids using external metrics (Creel and Preuschoft, 1976 , 1984 ) sorted hylobatid populations into primary species groupings which are in accordance with the four currently recognized generic‐level groupings. The goal of the current study was to assess the relative orientations of the orbits, palate, and basioccipital clivus among the hylobatid genera in an effort to further clarify whether the lesser apes differ significantly in these internal cranial features and how that variation patterns across the groups. Nine angular variables quantifying orbital, palatal, and basioccipital clivus orientations were measured on lateral view radiographs of adults representing three of the four hylobatid genera: Hylobates; Nomascus; and, Symphalangus. The interspecific adult hylobatid means for the angular variables were analyzed using t‐test contrasts. The total sample was further subjected to discriminant function analysis (DFA) to test for the ability of craniofacial angular variables to distinguish the hylobatid genera from one another. The three hylobatid genera displayed significant morphological differentiation in orbital, palatal, and posterior skull base orientations. Normal, jackknifed, and cross‐validation DFA procedures correctly identified the hylobatids 50–100% of the time. The observed morphological patterns generally mapped onto the findings of earlier external craniometric hylobatid studies and suggest concordance between specific internal and external cranial features. This article is the first comprehensive study of variation in internal cranial anatomy of the Hylobatidae and includes the first published craniofacial angular data for Nomascus. Am J Phys Anthropol 143:250–265, 2010. © 2010 Wiley‐Liss, Inc.